The present invention relates to a method and to an arrangement for determining angular velocities with the aid of an optical fiber ring interferometer, wherein the light waves passing through at least one optical fiber winding are sinusoidally modulated in phase and the amplitudes of several spectral lines of the interfering light waves exiting from the optical fiber are identified to yield the Sagnac phase shift which is proportional to the angular velocity.
A method and an arrangement of this type are disclosed in DE 3,140,110.A1. In the optical fiber of the ring interferometer forming an annular light path, two oppositely directed light waves propagate and interfere with one another upon exiting from the optical fiber. The interference is a function of the angular velocity with which the optical fiber, which forms at least one winding, is rotated. The angular velocity is proportional to the difference in phase between the two light waves that passed through the optical fiber in opposite directions.
This phase difference, it is called the Sagnac phase shift, can be determined, as disclosed in DE 3,140,110.A1, from the amplitudes of the spectral lines of the interference light leaving the optical fiber. The method according to DE 3,140,110.A1, according to which the Sagnac phase shift is determined from the amplitude of two spectral lines requires that the modulation index of the phase modulation occurring at the output of the light path is kept at a constant value by means of a control circuit.